This invention relates to convection ovens and particularly to gas-fired convection ovens employing recirculation of oven gases and burner combustion products.
Demand for convection ovens in the food service industry has increased substantially in the past ten years. Both gas-fired and electrically-powered units are available, and are used to cook a variety of foods such as cakes, pies, chickens, potatoes, and other foods. Even though performance of these two types has been relatively equal, electric convection ovens have enjoyed a considerably larger market share due to their lower selling price. The price advantage, which may exceed sixty percent, is due to the higher manufacturing costs of items such as side-mounted heat exchangers and combustion systems typically employed in gas-fired convection ovens.
One gas-fired convection oven of the recirculating type is disclosed in U.S. Pat. No. 4,108,139. That oven includes a mixing chamber which receives the combustion products of a burner and bottom outflow air collected from an oven cavity. The combined outflow of the mixing chamber is delivered to a blower and circulated back to the oven cavity through holes in a top manifold.
Other gas-fired convection ovens are shown in U.S. Pat. Nos. 3,710,775; 3,991,737; and 4,467,777. The first of these discloses an oven with a bottom-mounted burner whose combustion products travel in a duct to enter the lower portion of a hole in a partition plate ahead of a blower. Gases from the oven cavity enter the upper portion of the partition plate hole, and the blower recirculates the combined gas flow to re-enter the oven cavity through its front and sides.
In U.S. Pat. No. 3,991,737 a convection oven is described which includes an atmospheric gas burner in a combustion chamber in back of a blower which recirculates heated air through perforated side wall baffles. Gas flows are channeled in a manner such that as combustion products pass through a duct to the front of the blower to combine with oven gases they entrain a portion of gases flowing towards the oven exhaust.
The convection oven of U.S. Pat. No. 4,467,777 includes a rear-mounted burner which fires through a nozzle block in a forward direction towards a baffle which deflects combustion products back towards four blowers adjacent to the burner. Other baffles direct gases from the oven cavity to the blower inlet and direct gases exiting the blower to the front of the oven cavity.
While the above-referenced convection ovens and others currently in use provide certain advantages associated with recirculation, their structures are relatively complex and thus costly to manufacture. The prior art ovens also do not provide the temperature uniformity and level of efficiency desired in cooking certain foods.
Accordingly, it is an object of the present invention to provide an improved, low-cost gas-fired convection oven.
It is also an object of the invention to provide a high efficiency, gas-fired convection oven which produces cooking gases of uniform temperature distribution during operation.
It is a further object of the invention to provide a gas-fired convection oven which is easy to clean and service.
It is also an object of the invention to provide a compact, fuel-efficient gas-fired convection oven which operates without high external wall temperatures.
It is also an object of the invention to provide a direct gas-fired convection oven of the recirculating type of simple construction which does not require a combustion chamber or side wall heat exchanger.